The Optical Insert has been specifically designed for the PROTOS Integral Safety Glasses. It can be easily clipped to the bridge of the PROTOS Integral Safety Glasses. Your optician can easily mount optical lenses up to /-4 dioptres into the glass insert.  The lenses are fully protected, as they are placed behind the protective glasses. A major advantage of the integrated glass insert is that no temples interfere with the ear protector, and hence do not exert any uncomfortable pressure on the head.